Fittings, such as elbows and tees, for joining pipe elements together end-to-end, comprise interconnectable housing portions that are positionable circumferentially surrounding the end portions of pipe elements. The term “pipe element” is used herein to describe any pipe-like item or component having a pipe-like form. Pipe elements include pipe stock as well as fluid control components such as valves, strainers, restrictors, pressure regulators and the like.
An exploded view of an exemplary fitting is provided in FIG. 1. Each housing portion of the fitting has projections, also called “keys”, which extend radially inwardly and engage, for example, the outer surfaces of plain end pipe elements, pipe elements having a shoulder and bead, or circumferential grooves that extend around each of the pipe elements to be joined. Engagement between the keys and the pipe elements provides mechanical restraint to the connection and ensures that the pipe elements remain coupled even under high internal pressure and thrust loads and external forces. The housing portions define an annular channel or pocket, for example, a receptacle, that receives a seal, for example a ring gasket, typically an elastomeric ring which engages the ends of each pipe element and cooperates with the housing portions and the pipe elements to provide a fluid tight seal. A tube within the fitting extends between the ring gaskets to ensure that the entire fitting remains fluid tight. The housing portions have connection members, typically in the form of lugs which project outwardly from the housings. The lugs are adapted to receive adjustable fasteners, such as nuts and bolts, which are adjustably tightenable to draw the housing portions toward one another.
The projections on prior art fittings typically have arcuate surfaces with a radius of curvature that is substantially matched to the radius of curvature of the outer surface of the pipe element that it is intended to engage. For fittings used with grooved pipe elements, the radii of curvature of the arcuate surfaces are smaller than the radii of curvature of the outer surfaces of the pipe elements outside of the grooves so that the projections fit within and engage the grooves.
Methods of securing pipe elements together comprise a sequential installation process when fittings according to the prior art are used. Typically, the fitting is received by the technician with the housing portions bolted together, the ring gaskets and tube comprising the sealing element being captured between the housing portions of the fittings. The technician first disassembles the fitting by unbolting it, removes the ring gaskets, lubricates them (if not pre-lubricated) and places them around the ends of the pipe elements to be joined. Installation of the ring gaskets often requires that they be lubricated and stretched to accommodate the pipe elements. With the ring gaskets in place on the pipe elements, the tube is engaged with the ring gasket on each pipe element. The housing portions are then placed one at a time around the ring gaskets and tube, straddling the ends of the pipe elements. During placement, the housing portions engage the ring gaskets, the keys are aligned with the grooves in the pipe elements (when present), the bolts are inserted through the lugs, the nuts are threaded onto the bolts and tightened, drawing the housing portions toward one another, compressing the ring gaskets to effect a seal between the pipe elements, the tube and the fitting. The keys are engaged within the grooves in the pipe elements to provide mechanical constraint.
FIG. 2 shows a fitting 11 having first and second housing portions 13 and 15. The housing portions 13 and 15 are attached to one another by fasteners 17 and define a first receptacle 19 and a second receptacle (not shown). The first receptacle 19 defines an opening 21 for receiving a pipe element. The housing portions 13 and 15 are supported in spaced relation from one another on the outer surface of the seal 23 captured between the housing portions. This configuration is possible because the circumference of the outer surface of an undeformed seal 23 is greater than the sum of the circumferences of the surfaces on the housing portions with which the seal outer surface interfaces. When the housing portions are supported in this manner it is possible to insert pipe elements into the opening 21 between the housing portions without disassembling the fitting. However, there are some drawbacks to this solution to the problem of installing mechanical fittings. Note in particular that the seal 23 is distorted into an oval shape by the geometry of a close-fitting housing portion riding on at least a portion of the seal before the seal has properly seated in the pocket of the housing portion. If the degree of distortion of the seal is uncontrolled, the oval shape can result in pinching and damage to the seal.
As evident from the previous description, installation of fittings according to the prior art requires that the technician typically handle as many as thirteen individual piece parts, and must totally disassemble and reassemble the fitting. Significant time, effort and expense would be saved if the technician could install a fitting without first totally disassembling it and then reassembling it, piece by piece. Additionally, there is clearly a need for a pipe fitting with which the distortion of the ring seal may be controlled so as to avoid damage to the ring seal with which it is used, yet will also allow pipe elements to be inserted reliably without disassembly of the fitting.